1. Field of the Invention
The present invention relates to a tape-sheathing device for an electric wire, and particularly to a device for adhering a shielding tape to an electric wire and sheathing the electric wire to form a shielded wire for use in wiring electronics instruments such as a copy machine, a facsimile machine and the like, as well as in an automobile.
2. Description of Background Information
In general, since an electric wire for transmitting and receiving a control signal is influenced by other transmitting and receiving signals due to the influence of outside noise, and may cause a requisite control to become unreliable, a shielded wire is often used for an electric wire for control and the like. The shielded wire is generally produced by wrapping an electric wire in an axial direction with adhesive shielding tape. The shielding tape is made of an electro-conductive aluminum tape to be provided along the electric wire.
As shown in FIG. 7, a die 1 is usually used for wrapping the above-mentioned shielding tape of on electric wire. The die 1 has a tapered hole 1a. By simultaneously inserting the electric wire d and the shielding tape T into the tapered hole 1a, the electric wire d is wrapped with the shielding tape T due to the diameter-reducing effect of the tapered hole 1a, and the shielding tape T is adhered around the electric wire d to form the shielded electric wire sd. However, since only one die is insufficient to apply the pressure required for winding, problems have occurred in that the appearance of a wound tape is not uniform, coating does not reach completely around the electric wire, and the inner electric wire d is exposed.
For the above-mentioned problems, the present applicant has already proposed a technology for adhering a shielding tape on an electric wire and positively adhering to decorate, using the tape-sheathing device 5 of Japanese Patent Publication (Unexamined) Hei No. 10-3831 shown in FIG. 8.
The tape-sheathing device 5 provides a pressure roller unit 7, including a combination of two pairs of pressure rollers 8-1, 8-2 and 9-1, 9-2 which are mutually orthogonal at the downstream side of the feeding direction. A die 6 having the tapered insertion hole 6a is arranged at the upstream side in the feeding direction of the electric wire d and the tape T. Concave grooves 8a and 9a through which the electric wire d and the tape T pass are provided in the outer peripheral faces of the respective pressure rollers 8-1, 8-2 and 9-1, 9-2.
The electric wire d and the tape T are continuously fed in the direction of the arrow in FIG. 8 from the upstream side to the downstream side, in a condition in which the adhesive face Ta confronts the electric wire d. The tape T wraps the electric wire d in a width direction after passing through the die 6. When passing through the two combinations of pressure rollers 8-1, 8-2 and 9-1, 9-2, the tape T is pressed in turn by the grooves 8a and 9a of the respective rollers in orthogonal directions and in a diameter direction, and is wrapped and adhered on the electric wire d, thereby forming the shielded electric wire sd.
However, as the above-mentioned tape-sheathing device 5 presses the tape T by the two combinations of pressure rollers 8-1, 8-2 and 9-1, 9-2, the precision of groove position becomes important. Namely, when deviations and the like occur at the confronting respective groove positions, there are problems that the pressing direction relative to the tape T deviates, the tape T cannot be adhesively wrapped on the electric wire d, and the tape T peels off due to insufficient adhesion of the finished shielded electric wire sd.
On the other hand, when processing precision and installation precision are improved so as not to shift the respective groove positions of the pressure rollers 8-1, 8-2 and 9-1, 9-2, operating costs increase and the cost of the device itself increases. Further, even if a pressure roller having improved precision is used, there is a fear that the grooves and the like become worn by use with the lapse of time and the precision is lowered. Further, there is also the problem that daily maintenance for maintaining the precision is required.
The present invention was developed considering the above-mentioned problems, and an object is to cohesively and positively adhere a tape on an electric wire without using a press roller that requires precision.
In order to achieve the above-mentioned object, the present invention provides a tape-sheathing device for an electric wire, of wrapping an electric wire in the width direction of the tape in a condition in which the longitudinal direction of the tape is situated along the axial direction of the electric wire and is adhered to the electric wire. The tape-sheathing device includes a plurality of dies, with each die having a tapered hole at the downstream side in a feeding direction. The electric wire and the tape are fed by a feeding device and are jointly inserted into a respective one of the plurality of dies, which dies are provided in a serial arrangement in the feeding direction. The tapered hole of each of the dies other than the final die in the feeding direction is provided with an opening formed by notching an outer peripheral portion thereof, and each of the dies having the opening is arranged in a position with the opening shifted out of alignment relative to the respective opening of an upstream die. Thus, the tape is adhered while being wrapped around a portion of the electric wire whenever the electric wire and the tape pass through the respective dies.
Thus, a plurality of dies are used and the role of the respective dies is clarified. Thus, a tape for shielding or the like is adhered in a stepwise fashion on an electric wire and can be adhered on the electric wire without using a pressure roller. Namely, there is no pressing force at a notched portion on the respective dies due to notching a portion around the tapered insertion hole. On the other hand, the pressing force at a portion that is not notched is relatively increased.
Accordingly, the respective dies equipped with the openings due to notching are arranged in serial order so that the positions of the respective openings are not aligned, and the tape is adhered in a stepwise fashion on the electric wire by using only the final die where the opening is not provided. Therefore, the tape can be positively adhered to the electric wire by finally pressing the entire periphery of the taped wire again. As a result, the tape does not peel from the finished electric wire, and a high quality product can be produced. Further, since the present device does not use a pressure roller which requires high precision, costs are reduced and required maintenance and the like are unnecessary once the respective dies are arranged.
As the establishment of the specific die of the present device, the above-mentioned plurality of dies include three dies, namely a first die, a second die and a third die. The first die and the second die have a notched portion over about 90xc2x0 centering on the tapered hole in cross-section orthogonal to the axial direction at the outer peripheral portion of the downstream side in a feeding direction to provide openings in the tapered holes. The first die and the second die are arranged in a condition in which the respective openings are shifted relative to each other by about 90xc2x0.
In general, the width of the tape is established to be greater than the outer peripheral dimension of the electric wire so that the inner electric wire is not exposed once the tape has been adhered to the wire. Accordingly, as described above, the first die and the second die having the openings of about 90xc2x0 are arranged so that the respective openings are shifted by about 90xc2x0, and the third die having no opening is arranged as the final die. Thus, the tape can be positively adhered in a stepwise fashion on the outer periphery of the electric wire. Further, since the first die and the second die are provided with the openings by notching only an outer peripheral portion in the downstream side in the feeding direction, the electric wire and the tape are guided by the tapered hole having no notch at the upstream side and can be positively guided to the tapered hole having the opening at the downstream side.
In particular, the tape is adhered on a portion of the periphery of the electric wire from a first end in the width direction by the passage through the first die, and the remaining portion including a second end is in a condition in which it is separated from the electric wire without being wrapped. Then, another portion not wrapping the electric wire is adhered to the electric wire leaving unwrapped the area of the second end, by the passage through the second die. The area of the second end is finally adhered by passage through the third die, overlapping the area of the first end which was previously adhered. The entire periphery of the electric wire is pressed again and the tape is adhered to the electric wire. Therefore, peeling of the tape from the completed electric wire can be eliminated.
In another aspect of the present invention, A tape-sheathing device for an electric wire is provided. The device includes a plurality of dies, each die having a tapered hole that tapers from a large diameter at an upstream end to a smaller diameter at a downstream end, the plurality of dies being arranged in series along an axial line in a feeding direction. Each die, except the most downstream die in the feeding direction, has a notch in a peripheral portion thereof that communicates with the tapered hole, and the notch of each die is arranged out of alignment, in a radial direction of the axial line, from the notch of each other die. Thus, tape passing through each die is caused to be successively wrapped about only a portion of the electric wire as the tape and the electric wire pass through the series of dies, and the tape is completely wrapped by the most downstream die.
In other aspects of the present invention, the notch of each die of the tape-sheathing device may extend around about one quarter of the periphery of each die. Additionally, the plurality of dies may include first, second, and third dies, with the notches being provided in only the first and second dies. Moreover, each notch may extend around about one quarter of the periphery of each the die, and the notches may be aligned to be shifted about 90xc2x0 with respect to each other about the axial line.